Cooling arrangements for internal combustion engines provide the intrinsic function of cooling, for example, an internal combustion engine and further components of a motor vehicle and, where appropriate, utilizing the heated coolant as a heat source for heating devices of, for example, an air conditioning system of the motor vehicle. It is likewise important for these cooling arrangements that air which is included in the cooling circuit of the cooling arrangement be regularly removed from the circuit.
Thus, in general, a balancing tank is provided in the cooling arrangement. This serves, inter alia, for separating air from the cooling circuit, for compensating the increase in volume of the coolant during heating, for filling the cooling arrangement with coolant, and for building up a pressure cushion in order to prevent the coolant from boiling. In order to vent the cooling circuit, it is possible to incorporate the balancing tank both into the internal engine circuit and into the overall cooling circuit normally routed via a thermostat.
In order to enable the coolant to flow out of the internal engine circuit to a cooler and therefore into the overall cooling circuit, a thermostat opens when the internal combustion engine or the coolant has reached a minimum desired operating temperature. The coolant stream is conventionally driven by a pump which is driven by the internal combustion engine via the crankshaft. The throughput of the pump consequently depends on the engine rotational speed.
To ensure proper venting of the cooling circuit when the pump output capacity is low, a minimum flow velocity of the coolant inside the venting lines has to be maintained. On the other hand, when the pump output capacity is high, a maximum flow velocity inside the venting lines should also not be overshot, so as to avoid foaming of the coolant and therefore an intermixing of the coolant with air or excessive lowering of the coolant level in the balancing tank.
These requirements are usually achieved by means of fixed through-flow cross sections in the venting lines, in conjunction with suitably configured balancing tanks, for example by means of deflection or baffle surfaces arranged in the tanks, by a specific shaping of the balancing tank, by the arrangement of the coolant inlet and coolant outlet ports on the balancing tank, and by the coolant volume.
Thus, a cooling arrangement for an internal combustion engine is described, for example, in GB 2 458 263 A. The coolant is pumped through the internal combustion engine by means of a circulating pump. Between the internal combustion engine and the cooler, a thermostatic valve is arranged, which opens when the coolant temperature in the internal combustion engine overshoots a predetermined temperature. Furthermore, the inlet side of a balancing tank is connected via a coolant inflow line to an upper end of the cooler, and the outlet side of the balancing tank is connected to the suction side of the pump via a coolant return line. In specific operating states, to prevent coolant from undesirably flowing back into the balancing tank via the coolant return line connected on the outlet side, a nonreturn valve is provided on the outlet side of the balancing tank. Furthermore, in another embodiment, a throughflow limiter in the form of a pressure-limiting valve is arranged in the coolant inflow line between the cooler and the balancing tank. So the pressure-limiting valve maintains a stipulated coolant operating pressure upstream of the limiting valve, to be precise, in the cylinder head of the internal combustion engine, for example, in the event of an abrupt decrease in pressure in the cooling circuit on account of a sudden change in engine rotational speed.
Furthermore, GB 2 458 264 A discloses a throughflow limiter for use in a cooling arrangement for an internal combustion engine. It is proposed, in particular, to use the through-flow limiter described in a coolant inflow line of a coolant balancing tank.
GB 2 437 064 A discloses a degassing tank for an engine cooling system. The degassing tank has a conical shape and has one or more smaller degassing chambers arranged in it. The inlet and outlet ports for the coolant are in each case arranged tangentially with respect to the degassing tank. This arrangement is intended to make it possible to carry out the degassing of the cooling system by means of a compact degassing tank in which, moreover, only a relatively small coolant quantity is stored.
On account of the nowadays preeminent requirements regarding the configuration of the engine space which generally receives the cooling arrangements of a motor vehicle, for example the provision of pedestrian protection measures, the accommodation of complex drive trains and low weight, the available construction space is greatly restricted. It is therefore especially desirable to reduce the volume of the coolant balancing tank to a minimum.
The inventors herein have recognized the above mentioned issues and have devised an approach to at least partially address them. In one embodiment, a cooling arrangement comprises a coolant balancing tank having an inlet side and an outlet side, the inlet side connected via a first venting line to an internal combustion engine and/or connected via a second venting line to a cooler, and the outlet side connected via a coolant return line to an inlet side of a pumping device. At least one of the first and second venting lines has a flow control unit for variably limiting a coolant volume flow.
In this way, a cooling arrangement for an internal combustion engine, in particular for an internal combustion engine of a motor vehicle, is provided, which has essentially a coolant balancing tank which is capable of being filled with a coolant and the inlet side of which is connected via a first venting line to an internal combustion engine and/or via a second venting line to a cooler for cooling the coolant, and the outlet side of which is connected via a coolant return line to the inlet side of a pumping device for pumping the coolant through the internal combustion engine. Furthermore, a flow control unit for variably limiting the coolant volume flow is provided in the venting line or venting lines. Preferably, each of the venting lines has a (variable) flow control unit.
Thus, satisfactory venting of the cooling circuit under all possible operating conditions is ensured, particularly also when the pump output capacity is very low. This allows the use of a substantially smaller-volume coolant balancing tank with a simple internal set-up. Since the volume flow of the coolant can be varied by means of the flow control unit during operation, the operating range in which satisfactory venting of the cooling circuit is possible can be extended in a simple way. If the extended operating range is not utilized, the cooling arrangement disclosed herein likewise makes it possible to use, instead, a substantially smaller coolant balancing tank having a simpler set-up. This requires a smaller construction space and saves weight, since the disclosed coolant balancing tank stores a smaller coolant quantity on account of the smaller volume. Moreover, as a result of the smaller coolant quantity in the cooling circuit, the optimal operating temperature of the internal combustion engine, particularly after a cold start, is reached substantially more quickly.